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Crystal systems and Bravais lattices | Seven Crystal and Bravais Lattices

What is Crystal systems ?

If you are searching about crystal system then you are on the right place . Here i am sharing with you about crystal system.To represent the type of distribution of network points in space, seven different coordinate systems are required.These coordinate systems are known as crystal systems.

There are total seven crystal system are (1) Cubic (2) Tetragonal (3) Orthorhombic (4) Monoclinic (5) Triclinic (6) Rhombohedral (or Trigonal) and (7) Hexagonal . Crystal systems are named on the basis of geometrical shape and symmetry. In 1948, Bravais described 14 lattices are sufficient to describe all crystals.These 14 lattices are known as Bravais lattices and are classified into 7 crystal systems on the basis of cell parameters.

14 Bravais lattices of 7 crystal systems

Seven Crystal Systems and Bravais Lattices

Seven crystal system and Bravais lattices are described below 

1. Cubic crystal system : 

In this crystal system, the length of the unit cell edge is equal and at right angles to each other.for example a = b = c and α = β = γ = 90°.In simple cube lattice, lattice points or atoms are present at the corners of the cube. In a body-centered cube, atoms are present in the corners and an atom is completely present in the center of the cube. In the case of a face-centered cube, the atoms are present in the corners and in the center of all the faces of the cube.
Cubic crystal system

2. Tetragonal crystal system:

In this crystal system, two lengths of unit cell edges are equal while the third length is different. Three edges perpendicular to each other. for example a = b ≠ c and α = β = γ = 90°.Examples for tetragonal crystal system is TiO2, SnO2,

Tetragonal crystal system

3. Orthorhombic crystal system:

In this crystal system, the unit cell edge lengths are different and they are perpendicular to each other. For example a ≠ b ≠ c and α = β = γ = 90.There are four Bravais lattices in this shown below in given figure.They are simple, face centered, body centered and base focused. Examples of orthorhombic crystal systems are BaSO4, K2SO4, SnSO4, etc.

Orthorhombic crystal system

4. Monoclinic crystal system

In this crystal system, unit cell edge lengths are different. Two unit cell edges are not perpendicular, but they are perpendicular to the third edge. For example, a ≠ b ≠ c; α = γ = 90° ≠ β.This crystal system has only two Bravais lattices shown in given figure . Example of Monoclinic crystal system are CaSO4.2H2O (gypsum), Na3AlF6 (cryolite), etc

Monoclinic crystal system

5. Triclinic crystal system:

In this glass system, the length of the edge of the unit cell is different and not perpendicular. for example a ≠ b ≠ c and α ≠ β ≠ γ ≠ 90° and all angles are different .Examples for triclinic crystal system are K2Cr2O7, CuSO4. 5H2O, etc

Triclinic crystal system

6. Rhombohedral [ Trigonal] crystal system: 

In this crystal system, unit cell edges are all lengths equal. The angles between the axes are the same but other than 90°.i.e. a = b = c and α = β = γ ≠ 90°.Examples for Rhombohedral crystal system are As, Bi, Sb, etc

Rhombohedral [ Trigonal] crystal system

7. Hexagonal crystal system:

In this glass system, two sides of the unit cell edge length are equal and the angle between these edges is 120 °. These two edges are perpendicular to the third edge and are not the same length. Bravais lattice is primitive only

Hexagonal crystal system


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